Sikorsky and Lockheed Martin’s resolution to construct a hybrid tilt-wing know-how demonstrator is a big step ahead for eVTOL plane. We’re in a novel place to say this, as Dufour Aerospace has been designing, constructing, and testing tilt-wing plane for a few years.
We’ll current a number of the causes that we consider Sikorsky has made the suitable alternative in creating a tilt-wing, together with hover, transition, cruise effectivity, easy transition, robustness, scalability, and naturally security.
What’s a tilt-wing plane?
Not like tilt-rotor or tilt-propeller plane, a tilt-wing tilts the entire wing as a substitute of simply the propeller nacelles. Whereas this will likely appear a small element, it’s truly a basic distinction.
Tilt-wing plane will not be new – they had been designed, constructed, and intensively flown within the 60s and 70s of the final century, at a time when distributed propulsion and superior digital management programs weren’t but obtainable. Distinguished representatives of this primary tilt-wing wave are the American XC-142 and the Canadian CL-84 plane.
Hover and transition effectivity
Tilt-rotor and tilt-propeller plane lose a few of their thrust throughout vertical take-off and touchdown as a result of the mounted horizontal wing blocks the airflow. This lack of thrust is named “obtain”. The presence of the wing is a drawback for the plane till it has accelerated past a essential velocity.
Tilt-wing plane, in distinction, hold the wing aligned with the propeller thrust. This minimizes obtain and drag, and the airflow energizes the wing, producing further raise as quickly because the plane begins to maneuver ahead.
This attribute is a big benefit for the general energy necessities and configuration of the plane.
Easy transition with giant security margins
Transitioning from hover to ahead flight and vice versa in lots of VTOL configurations is aerodynamically complicated and energy-intensive. The lean-wing design simplifies this transition. By rotating the entire wing ahead, the tilt-wing seamlessly converts from a vertical to a horizontal configuration, with out drastic adjustments in airflow. There isn’t any handover between a hover propulsion system and a cruise propulsion system as is the case with lift-and-push configurations. This interprets to smoother, seamless transitions.
Because the wing offers raise always, the facility necessities for transition are dramatically decrease than with every other convertible idea, leading to excessive effectivity. There are additionally giant energy margins remaining for management and a large hall within the flight envelope, which interprets on to giant security margins always.
Cruise effectivity
As an eVTOL plane flies 90% of the time in cruise configuration, it’s important that the plane is as environment friendly as attainable in cruise. Effectivity comes with what is named a “clear” configuration – as little drag as attainable. Some VTOL configurations, resembling lift-and-push, carry the burden of non-lifting parts (resembling propellers which might be solely used for hover) throughout cruise flight. These parts create drag, decreasing the general effectivity. Everybody who ever flew a propeller plane with velocity brakes is aware of the affect of drag. The lean-wing design may be very clear in cruise, so doesn’t undergo from this disadvantage. So the tilt-wing plane is a fuel-efficient long-range cruiser, which can also be able to VTOL operations.
Mechanical simplicity and robustness
Hinges on VTOL plane are essential parts but additionally signify potential weak factors. They have to be strong and redundant. Dropping a hinge in flight and potential cascading failures are a danger that must be eradicated as a lot as attainable.
Vital hinges are designed to be multi-loadpath and harm tolerant in order that there isn’t any single level of failure. This can be a well-known design precept in aviation, and is used for instance on the horizontal stabilizer trim mechanisms of all business airliners. (These trim mechanisms are designed and licensed a lot the identical means as our wing tilt system.)
Constructing hinges on this rock-solid means provides weight and inspection necessities, in fact. So it is a bonus to have a single hinge, because the tilt-wing does, somewhat than a number of hinges as in a tilt-propeller design.
Dealing with qualities
When speaking about security, most representatives of the eVTOL scene are virtually completely speaking about part certification. There may be little or no dialogue of what issues equally as a lot: the flight conduct and management margins of the plane.
Technical failure of a part is never the rationale for an accident. 80% of the accidents are brought on by human error – a pilot mistake. So it’s essential that pilots (and automatic flight management programs) have sufficient management margin to react if one thing unexpected occurs.
A direct studying of Dufour Aerospace’s CEO, Thomas Pfammatter, with over 30 years of expertise in helicopter operations, is that having giant management authority margins is a key ingredient for security.
That’s the place tilt-wing plane excel. The propellers and totally energized wing with aerodynamic management surfaces present highly effective and direct management authority in all three axes. Moreover, the flexibility to regulate the wing to any given wind state of affairs permits for redundant management and easy transitions whereas conserving the cabin stage.
This isn’t simply concept: it has been confirmed and examined by a whole bunch of check and armed forces pilots with the CL-84 and XC-142 plane, and by Dufour Aerospace in check flights virtually day-after-day.
Scalability
The air behaves in another way at completely different scales. What works for a multicopter drone, a “flying brick”, doesn’t work so nicely for bigger plane. Whereas multicopters, lift-and-push, and tilt-propeller plane wrestle to scale up, tilt-wing plane can comfortably be a lot bigger. This has been confirmed by the XC-142 at over 20 tons, and is because of the effectivity of the blown wing.
That makes the tilt-wing idea distinctive in its means to cowl the largest vary of transitional plane at an inexpensive value.
Conclusion
At Dufour Aerospace, we’re nicely conscious of some great benefits of the tilt-wing configuration, as we have now been constructing and flying tilt-wing plane for a few years, so we perceive the explanations behind Sikorsky’s resolution.
They’ve additionally determined to pursue a hybrid energy strategy, somewhat than utilizing solely batteries for power storage. Electrical propulsion has many benefits, together with noise discount and redundancy. Nonetheless, at present’s battery know-how doesn’t come near the particular power obtainable in gasoline. The hybrid energy configuration will enable Sikorsky to convey collectively the perfect of each of those applied sciences, and obtain for much longer vary missions, and higher operational versatility, simply as we do at Dufour Aerospace.
From our staff at Dufour Aerospace to yours, congratulations, Sikorsky!
